Paper manufacture



15, 1936. I CARROLL 2,064,647

PAPER MANUFACTURE Filed Jan. 11, 1936 J INVENTO (W m? MGQ.

ATTORNEY.

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Application .llnary 11, 1936, Sell No. d,;72d

This invention relates to improvements in paper manufacture and isdirected more particularly to improvements in apparatus for and methodsof drying paper.

5 The principal objects of the invention are the provision of apparatusfor and methods of drying paper to facilitate the making of paper havingboth its surfaces more nearly uniform than has heretofore been possible.

The type of dryer with which the invention is concerned includes aplurality oi rotatable spaced hollow drying cylinders, commonly calledcans, which are arranged in upper and lower banks or rows. A heatingmedium such as steam is delivered into the cylinders and the condensateis led therefrom.

The web of paper to be dried is led into the wet end of the machine andit travels over a roll of one bank or row and then over a roll of theother bank or row. That is, the web alternately contacts the rolls ofthe two banks or rows so that first one of its sides, and then theother, contacts with the rolls.

As is well known, a paper web has a felt side and a wire side. Thelatter is that side next to the Fourdrinier wire as the paper isformedpthe former is the side next to the felt. The wire side of thepaper is relatively smooth as compared with the felt side, whereforthere is a dif-' n ference in the rate of drying between the two sidesThat is, the relatively smooth or wire side of the paper contacts moreperfectly with the drying cylinders than does the less smooth or feltside with the result that there is a difference in the drying rate whichproduces paper having unlike surfaces. To overcome this varioussubsequent operations on the paper are necessary.

In the operations of dryers of the type referred to, it has been thecommon practice to divide the cylinders into groups or sections and toheat the rolls of the, difierent sections at diiferent temperatures butthis does not overcome the difierence in the drying rate existingbetween the felt and wire side of the paper.

According to this invention, however, the difference in the drying rateis overcome by heating some of the rolls of one'bank at one temperaureand the adjacent rolls of the other row 'or bank at a differenttemperature. Then the paper travels alternately over rolls of a certaintern;- perature and rolls of a diflerent temperature. The temperaturesare so controlled, according to, the invention, that the side of thepaper requiring the most heat contacts with cylinders of (oi. sa -2e) atemperature higher than that of the other cylinders with which the otheror faster drying side of the paper contacts. This facilitates theproducing of paper which is substantially uni-- form on both sides; thatis paper having more 5 uniform characteristics on opposite sides.

Various other novel objects and advantages of the invention will beobserved from the following description or the present preferred formthereof, reference being had to the accompany- 10 ing drawing wherein:

The figure isa small scale diagrammatic elevational view of a dryingapparatus emb certain novel features of the invention.

Now by reference to the drawing more in de- 35 tall, the invention willbe fully described.

The dryer of the type to which the invention relates includes upper andlower banks or rows of cylinders or drums, commonly called cans. Thecylinders are hollow and are mounted for 20 rotation so that a web Prepresented by dot-dash lines is carried alternately over a roll of theupper bank and over a roll of the lower bank and thereby through themachine in the direction of the arrow a. 25

A heating medium such as steam is delivered into the cylinders and thecondensate leads from the rolls. Sometimes the steam is delivered intoone end of the cylinders while the condensate is taken out at the otherend and in other cases the steam and condensate return are at the sameend of the cylinder.

Suitable stumng boxes and connections are provided to facilitaterotation of the cylinders and form no part of the present invention. Forclearness, as will appear, the drawing shows the heating medium pipes atone end of the cylinders while the return, or condensate, pipes are atthe other.

According to the invention, asmali number of the rolls such as 2 of theupper bank at the wet end of the dryer are operated at a difierenttemperature than that of a plurality of adjacent rolls such as t of thelower bank.

This is accomplished by the provision of sepa- 5 rate headers B and 8 tosupply the heat to the upper and lower cylinders. The headers 6 and 8are connected by pipes ill and I2 to a main supply pipe it carrying theheating medium such as steam. Valves it and 16 in pipes ill and I2control the flow of steam into the headers 6 and 8. The headers 6 and 8are connected to the cylinders 2 and 4 by pipes I8 and 20.

Other drainage headers 22 and 2d are connected by pipes 26 and 28 to thecylinders and these headers are provided for the condensate. They areconnected, as by pipes 30 and 32, to a drainage system in associationwith which there may he means such as a vacuum pump to bring about a lowpressure condition.

As stated, the valves Ill and I2 control the flow of steam to thecylinders so that the upper rolls may be operated at differenttemperatures than that of the lower rolls. The temperature of one groupof rolls may be relatively greater or less than that of the other group,and either the upper or lower group may carry the relatively highertemperature, depending upon the type of paper being handled, the dryingeffect necessary or desired, and other variable factors.

As an example, a certain type of paper may enter the dryer so that itsrelatively smooth wire side contacts with the upper rolls while itslower less-smooth side, which requires relatively more heat, contactswith the lower rolls. Under these' conditions the lower rolls may beoperated at the desired and necessary higher temperature relative tothat of the upper rolls by controlling the flow of steam to headers 6and 8.

In this way, at the wet end of the dryer where the initial drying of thepaper takes place it is possible to provide the difl'erence intemperature of the upper and lower rolls in order to overcome thedifficulties and objections inherent when there is a difference in thedrying rate of opposite sides of the paper.

Other upper cylinders 3 and 3' and lower cylinders 5 and 5' may beprovided. Of course, there may be any desired number of cylinders forsupporting and acting on the paper.

The rolls 3 and 5 constitute one group or section and the rolls 3' and5' constitute another group or section. The rolls may be arranged ofcourse to provide a desired number of sections. Steam supply headers 40and 42 are connected by pipes 44 and 46 while steam is carried to thecylinders by pipes 48 and 50. Control valves 52 and 54 in pipes 44 and46 control the flow of steam into the headers.

Return headers 56 and 58 are connected to the cylinders by pipes 60 and62 and pipes such as 64 and 56 are provided for drainage and may beconnected to a vacuum pump or the like.

The valves l4, I6, 52, and 54 may take any temperature of the condensatein the headers and this may be accomplished by means of atemperature-sensitive substance operatively associated with the returnheaders and carried by conduits 68, 10, 12, and 14 which are connectedto the control valves. A valve apparatus of the general type disclosedin United Stata Letters Patent to Lear 1,965,552 and dated July 3, 1934,with the necessary modifications will sufllce for this part of theinvention Thus it will be seen that the paper to be dried is initially.led over cylinders of different temperatures in such a way that oppositesides thereof alternately contact with cylinders of diflerenttemperature whereby the difference in the drying rate or ability to dryof the opposite sides of the paper is overcome or at least largelyobviated.

While I have described. the invention in great detail and with respectto a preferred form thereof, it is not desired to be limited theretosince many changes and modifications may be made therein withoutdeparting from the spirit and scope of the invention. What it is desiredto claim and secure by Letters Patent of the United States is:

1. The method of drying paper which consists in, contacting oppositesides of a web of paper alternately with the cylinders of upper andlower spaced banks of cylinders, maintaining a certain portion of thecylinders of the lower bank of cylinders at a certain temperature and aportion of the cylinders of the upper bank adjacent to said certainportion of the lower bank with which the web first contacts at adifferent temperature and maintaining other subsequent cylinders of thebanks which are adjacent one another at substantially the sametemperature.

2. The method of drying paper which consists in, leading a web of paperinto the leading in end. of a dryer including spaced upper and lowerrows of hollow drying cylinders so that said web has its opposite sidescontacted alternately with cylinders of the upper and lower rows ofcylinders, maintaining a certain number of the cylinders of one row atsubstantially one certain temperature and adjacent cylinders of theother row at substantially a different temperature, whereby one side ofthe web contacts cylinders of one temperature and the other side of saidweb contacts cylinders of a different temperature.

3. The method of drying paper which consists in, leading a web of paperinto the leading in end of a dryer including spaced upper and lower rowsof hollow drying cylinders so that said web has its opposite sidescontacted alternately with cylinders of the upper and lower rows ofcylinders, maintaining a certain number of the cylinders of one row atsubstantially one certain temperature and adjacent cylinders of theother row at substantially a different temperature, whereby one side ofthe web contacts cylinders of one temperature and the other side of saidweb contacts cylinders of a different temperature, and in maintainingsubsequent cylinders of the upper and lower rows at substantially thesame temperature. 1

' GEORGE S. CARROLL.

